1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and a method of manufacturing the LCD, and more particularly, to a fringe field switching (FFS) mode LCD having a wide viewing angle characteristic whose outdoor readability characteristic and screen quality are improved in a transmissive mode, and a method of manufacturing the FFS mode LCD.
2. Discussion of Related Art
An FFS mode LCD has been developed to improve a low aperture ratio and transmittance of an in-plane switching (IPS) mode LCD.
In the FFS mode LCD, a common electrode and a pixel electrode are formed of a transparent conductor to enable a higher aperture ratio and transmittance than the IPS mode LCD. Also, a distance between the common electrode and the pixel electrode is smaller than a distance between upper and lower glass substrates to generate a fringe field between the common electrode and the pixel electrode and operate all liquid crystal molecules as well as liquid crystal molecules existing in upper parts of the electrodes. As a result, the FFS mode LCD can have improved transmittance. Conventional art relating to the FFS mode LCD has been disclosed in, for example, U.S. Pat. Nos. 6,256,081 and 6,266,118.
Such a conventional FFS mode LCD includes: a lower substrate including a plurality of pixels consisting of a transparent pixel electrode, a transparent common electrode and a thin film transistor (TFT); an upper substrate consisting of a color filter formed of red, green and blue color filter patterns arranged by turns to correspond to the pixels; and a black matrix (BM).
Together with the transparent common electrodes, the transparent pixel electrodes generate an electric field to control transmittance operating a liquid crystal molecules interposed between the lower and upper substrates.
Meanwhile, LCDs are generally classified into a transmissive LCD using a backlight and a reflective LCD using natural light as a light source. Since the transmissive LCD uses a backlight as a light source, it is possible to provide bright images in a dark environment. However, the transmissive LCD has high power consumption due to the backlight and poor outdoor readability. On the other hand, the reflective LCD uses surrounding natural light as a light source without a backlight, thus having low power consumption and being usable outdoors. However, the reflective LCD cannot be used in a dark environment.
To solve these problems of the conventional transmissive LCDs and reflective LCDs, an advanced FFS (AFFS) mode LCD (a new FFS mode LCD) that is a transmissive FFS mode LCD having improved indoor and outdoor readability has been suggested in a paper “A Novel Outdoor Readability of Portable TFT-LCD with AFFS” (K. H. Lee et al., SID 06, 2006, p 1079) written by the present applicant.
According to the AFFS mode LCD, an electric field is appropriately generated at the interface region between a slit and a bar of a pixel electrode, and thus a liquid crystal is smoothly operated. However, in the middles of the respective slit and in the middles of bars, a distance between operating electrodes increases, and the intensity of the electric field decreases. Furthermore, in these regions, the direction of electric field is not continuous (abruptly changed). Thus, the liquid crystal is not smoothly operated and disclination occurs. These problems need solutions. In particular, the problems cause non-uniform alignment of the liquid crystal and deteriorate screen quality at high voltage.
In addition, a reflective region is formed to increase outdoor visibility, and internal reflection increases outdoor brightness. However, since other regions except for an opening region (aperture region) are used as the reflective region, the reflective region is not large and its effect is not good enough.